US 3104232 A
Description (OCR text may contain errors)
United States Patent 3,104,232 POLYETHYLENE COMPOSITIONS CONTAINING N-ALLYL FATTY ACID AMIDES Clayton F. Clark, Saxonville, Mass, and Robert W. Hill,
Leawo'od, Kans., assignors to Spencer Chemical Company, Kansas City, Mo., a corporation of Missouri No Drawing. Original application June 18, 1958, Ser. No. 742,755, now Patent No. 2,991,265, dated July 4, 1961. Divided and this application Aug. 30, 1960,
Ser. No. 52,785
This invention relates to plastic compositions and, more specifically, to novel polyethylenes of enhanced slip characteristics.
This application is a division of our copending application Serial No. 742,755, filed June 18, 1958, now US. Patent No. 2,991,265.
Polyethylene is one of the most popular and Well known thermoplastics of this plastic age. The number of varied uses increases spectacularly each year; many of these include the utilization of polyethylene films. Polyethylene film is being used to package a wide and varied list of commercial commodities such as foods, meats, chemicals, pharmaceuticals, seeds, clothing, hardware, toys, etc. One of the more important properties associated with polyethylene film is its slip or film-to-film coefficieut of friction. Slip, as it is known to the .trade, relates to the resistance of the film to a sliding action over another film surface or over a metal surface, as manifested by the thin sheets of blown film sticking to one another. Poor slip characteristics of polyethylene film are especially troublesome to users of automatic packaging equipment. Poor slip is a greater problem with blown film, which is usually thinner than extruded sheets, although there are also many applications of sheets in which an improved slip is also advantageous.
The object of this inventon is to provide plastic compositions having an improved slip or low film-to-film coefficieut of friction. A further object of this invention is to provide polyethylene compositions which, upon conversion to sheets or films, have an improved slip. A still further object of this invention is to provide polyethylene films or sheets possessing improved slip characteristics.
There is provided by this invention novel plastic compositions comprising polyethylene containing a small amount of an additive which enhances the slip of the polyethylene. Additives which have been found to enhance or improve the slip of polyethylene when incorporated therein are the N-oleyl derivatives of fatty acid amides in which the aliphatic moiety of the fatty acid is a higher aliphatic group of 9 to 21 carbons, saturated or unsaturated, such as the alkyl and alkenyl groups, and advisably having an odd number of carbons. The aliphatic group is preferably a straight chain. Some of the compounds of this type which are useful are N-oleyl capramide, N-oleyl mynstamide, N-oleyl stearamide, N- oleyl erucamide, N-oleyl palmitamide and N-(n-oley1)- oleamide. The additives also advisably have a melting point of less than 69 C.
Additives of the described types are solids at room temperature, insoluble in water and soluble in most hot hydrocarbons. These compounds are readily prepared by conventional processes such as by heating the appropriate fatty acid with the appropriate amine at about ice Incorporation of the additive in the polyethylene may be effected by several different methods. For example, the additive may be added as a solid, in solution or in the form of a slurry to polyethylene in either the molding powder or pellet form followed by tumbling and drying. The additive may also be incorporated by melt blending the ingredients in a conventional apparatus, such as a banbury mixer, heated rolls or a plasticater;
Additives of the described types are effective slip agents when incorporated in polyethylene to give a polyethylene composition containing about'0.0l% to about 1% by weight of .the additive. The preferred composition is about 0.05% to about 0.2% by weight of additive in polyethylene. Although more than 1% of additive may be incorporated in polyethylene, larger amounts would not generally be warranted.
It is to be understood that minor amounts of other desirable materials, such as high melting waxes, antioxidants, dyes and pigments, lubricants, antistatic agents, and the like, may also be present in amounts which do not affect the high slip properties of these polyethylene compositions.
The described additives are effective in improving the slip characteristics of all types of polyethylene, Whether they be the more linear polyethylenes prepared by the low pressure process, the conventional high pressure process polyethylenes of a lower density or the medium density polyethylenes.
Although polyethylene containing one or more of the described additives is particularly useful for improving the slipof products fabricated by extrusion into thin films, sheets, blown tubing, and the like, it may also be cast or molded into films, sheets, rods, tubes and piping,
, filaments, and other shaped articles, having better slip than similar products made of polyethylene containing no additive. In this regard, molded articles such as cups which tend to stick together when nested are more readily separated when the polyethylene contains at least one of the described additives. The polyethylene compositions of this invention may also be used for coating paper, cloth, Wire, metal foil, glass fiber mats, synthetic and natural textiles, etc., where good slip is desired.
Polyethylene to which at least one of the additives is added has improved blocking properties, that is, film made from such polyethylene has much less tendency to block than an identical polyethylene containing no additive.
The following example illustrates the improved effect of the additives on the slip of polyethylene sheet.
EXAMPLE 1 Various additives of the described group were introduced singly into a commercial high pressure process type polyethylene having a density of 0.92 and melt index of 2 by introducing the additives into a commercial type banbury and banburying for 10 minutes at F. The
polyethylene Was then sheeted on a roll mill, ground on a Wiley mill and screened through a screen having 4 mm. openings and extruded into fiat film on a 1-inch extruder equipped with a 6-inch fiat film die. The film was aged by suspending in air at room temperature for at least 24 hours. The film was evaluated for slip by means of an inclined plane method, which consisted of stretching the film on an adjustable plane. A metal sled weighing 95 grams was placed on the film and one end of the plane then raised until the sled began to slide. The slope 10 of the plane at this point, expressed in degrees, was reported as the slip of the additive. The following results were obtained:
Table Additive Formula 80 iii at 0.05%, degrees 0 N-olcylcapramide OH3(CH; )a( i-NHCmHss O N oleylmyristarnide CH;(CHz)1z NH-C1aHa5 19 O N-olcylpalmitamlde CHa(CHr)n('L -NH-CiaHa5 23 O N-oleylstearamide CHKCHflmJ-NH-CmHss 27 O N-olcylerucamide OH3(CH2)1CH=CH(CHz)nJi-NH-CmHaa 12 N-(n-oleyDoleamide C17H33 NH-(OH2)8OH CH (CH2)7CH3 25 Control (no additive) 36 The results clearly show the improved slip characteristics of the polyethylene-additive compositions. The control containing no additive required an angle much higher than the polyethylene-additive compositions in order to cause the sled to slide. We have found that polyethylene compositions which have a low film-to-metal coetficient of friction will also have a comparably low film-to-film coeificient of friction.
Various changes and modifications of the invention can be made and, to the extent that such variatioins incorporate the spirit of this invention, they are intended to be included within the scope of the appended claims.
What is claimed is:
1. A plastic composition comprising polyethylene and from 0.01% to 1.0% by weight of N-oleyl stearamide.
of a fatty acid amide, said N-monoleyl fatty acid amide having the formula References Cited in the file of this patent FOREIGN PATENTS 1,132,791 France Nov. 5, 1956